Abstract Particle image velocimetry (PIV) technique was adopted to understand material flow and measure strain rate around the tool pin during friction stir welding (FSW). The micro-spherical glass tracers in a transparent visco-plastic material, of almost similar densities, were used as experimental materials. The characteristics of material flow, in particular, flow velocity and strain rate were obtained by following the path of the tracer particles. A rotational zone around the tool pin was observed due to large deformation of the material close to the tool pin. The maximum velocity was noted to be 60% (close to the pin surface) of the pin peripheral velocity, and strain-rate was found to be 20 s−1 (0.6 mm away from the pin periphery) at FSW parameters of 170 rpm and 50 mm min−1. The strain rate was found to increase from 8 s−1 to 44 s−1 with increase in rotational speed from 75 rpm to 425 rpm. Predictive correlations were established for variations of velocity and maximum strain-rate as a function of rotational, traverse speeds and distance away from the tool pin surface. Overall, it was established that PIV technique can be utilized for the understanding of material flow and strain-rate behaviour during FSW. Furthermore, this technique enabled in-situ visualization overcoming drawbacks of other techniques reported in the literature.

中文翻译：

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搅拌摩擦焊过程中材料流动的可视化和应变率的确定

摘要 采用粒子图像测速（PIV）技术来了解材料流动并测量搅拌摩擦焊（FSW）过程中工具销周围的应变率。密度几乎相似的透明粘塑性材料中的微球玻璃示踪剂被用作实验材料。通过跟踪示踪粒子的路径获得材料流动的特性，特别是流速和应变率。由于靠近工具销的材料的大变形，观察到工具销周围的旋转区。注意到最大速度是销圆周速度的 60%（靠近销表面），并且发现应变速率在 170 rpm 和 170 rpm 的 FSW 参数下为 20 s-1（远离销圆周 0.6 mm）。 50 mm min−1。发现应变速率随着转速从 75 rpm 增加到 425 rpm 从 8 s-1 增加到 44 s-1。为速度和最大应变率的变化建立了预测相关性，作为旋转、横向速度和距工具销表面距离的函数。总体而言，已确定 PIV 技术可用于了解 FSW 期间的材料流动和应变率行为。此外，该技术实现了原位可视化，克服了文献中报道的其他技术的缺点。已确定 PIV 技术可用于了解 FSW 期间的材料流动和应变率行为。此外，该技术实现了原位可视化，克服了文献中报道的其他技术的缺点。已确定 PIV 技术可用于了解 FSW 期间的材料流动和应变率行为。此外，该技术实现了原位可视化，克服了文献中报道的其他技术的缺点。